In a dry etching apparatus using plasma such as a RIE (Reactive Ion Etching) apparatus, deposits adhere to an inner wall of a reaction chamber when a substrate is processed. When these deposits are accumulated, the deposits may adhere as particles onto substrates that are subsequently processed. If the deposits adhere onto the substrates, patterns as designed are not formed on the substrates, thereby becoming a cause of a malfunction.
To suppress adherence of these deposits to the inner wall of the reaction chamber, a confinement ring that separates between a plasma generation region in the reaction chamber and the inner wall of the reaction chamber is sometimes provided. The confinement ring suppresses the adherence of deposits to the inner wall of the reaction chamber and also suppresses deposits having adhered to the inner wall of the reaction chamber from inversely penetrating into the plasma generation region to adhere onto the substrate.
However, when an end point of etching processing is to be detected based on a plasma emission intensity, the confinement ring becomes an obstruction while light of plasma emission is collected, and thus becomes a cause of interference to detection of the plasma emission intensity. Therefore, it is sometimes difficult for an etching apparatus having the confinement ring to accurately detect the end point of etching processing.